88 Transactions of the 



The Mica Schist runs in a thin band northwards, where it expands 

 into a large surface, on whicli the Hill of Saxaford stands. It is of a 

 greenish colour, but often becomes dark and talcose, and is intersected 

 by quartz veins. It thus differs from the micaceous gneiss of 

 Woodwick, which is brown. 



The projecting points of land, known as Lanibaness and Skaw, are 

 composed ot gneiss, and stand out against the sea. 



The Loch of Cliff, or North Lake, is geologically interesting as 

 lying on a very pure crystalline limestone. This rock is best seen on 

 its eastern side, where it has been quarried for calcination. On the 

 other side of the lake it cannot be seen. It is traced in a narrow 

 band as far as Coldbacks, where it disappears. It used also to be 

 quarried for lime on the south of Baliasta. Its strata are very 

 distinct, dipping eastward, at an angle varying from 60° to 70". The 

 line of strike isui a N.N.E. and S.S.W. direction. No traces of fossils 

 have yet been discovered in it ; its stratigraphical age is therefore only 

 conjectured. It contains much carbonate of lime, in the form of 

 white streaks. The section across seems to confirm the theory that 

 the serpentine is, possibly, metamorphosed limestone. At the northern 

 end of Cliff Loch, quartz rock is found in abundance. 



The Diallage rock, or Euphotide, lies in contact with the eastern 

 side of the serpentine, and, near the junction, appears to cross it in 

 abrupt masses, but no decided gradation between the two rocks can be 

 recognized, the junction being always distinct. The rugged form of 

 Balta Island best illustrates its external aspects, for it is slowly acted 

 on bv the atmosphere, owing to its natural hardness and compact 

 structure. In colour the diallage varies from light green to black, 

 and weathers grey. As before noticed, it yields a comparatively good 

 herbage. It contains amianthus and asbestos. 



The Chlorite Schist occupies the south-east corner of the island, and 

 unites with the diallage near Uya. It is of dark green colour, and 

 is intersected by numerous quartz veins. At its eastern extremitj^, 

 patches of the serpentine and diallage again crop out. 

 I believe the Island of Uya also to be composed of this schist, but I 

 had not an opportunity of visiting it. 



There are no distinct signs of glaciation in this island, boulders 

 being absent, and no glacial clay occurring round the shores. I must 

 not, however, omit mentioning a large rounded stone which lies on the 

 surface of the ground, by the road side near Uya. 



Minerals. — Unst is of great mincralogical celebrity. Most of its 

 minerals are rare, and two of them are peculiar to itself in the list of 

 British minerals. 



The most important in value is the above-mentioned chromale of 

 iron, though its mines seem almost exhausted, and its actual extent is 

 still a point of discussion. 



Perhaps the hydrate of magnesia should rank next in value as a 

 museum mineral, and for use in the arts, the chrome ochre of Unst 

 must be next considered. This is found around Balta as a clayey sub- 

 stance, occurring in a pulverulent state, in loose earthy masses, of a 



